Wireless communication networks are ubiquitous, and are becoming increasingly complex as new standards and protocols are established to increase the number of subscribers, data rates, efficiency, and the number and variety of services delivered to subscribers.
One representative example of a modern wireless communication network standard is the Long Term Evolution (LTE), defined by the Third Generation Partnership Project (3GPP). FIG. 1 depicts a functional block diagram of a LTE network, including a core network (i.e., the evolved packet core) and a Radio Access network (i.e., the Evolved Universal Terrestrial Radio Access Network, or E-UTRAN). The evolved packet core network nodes include those having the functionality of a Mobile Management Entity (MME) and a Signalling Gateway (S-GW). The E-UTRAN nodes include evolved Node B's (eNB). The eNBs connect to each other over the logical X2 interface, and to the MME/SGWs over the logical S1 interface.
A representative management system is shown in FIG. 2. The node elements (NE), also known as an eNodeB or eNB, are managed by a domain manager (DM), also referred to as the operation and support system (OSS). A DM may further be managed by a network manager (NM). Two NEs are interfaced by X2, whereas the interface between two DMs is referred to as Itf-P2P. Note that, although embodiments of the present invention are described herein with respect to 3GPP LTE, the invention is applicable to any wireless communication network protocol (e.g., WCDMA, GSM, WiMAX, etc.).
The management system may configure the network elements, as well as receive observations associated to features in the network elements. For example, DM observes and configures NEs, while NM observes and configures DM, as well as NE via DM. Thus, the management system is hierarchical, with a high-level NM receiving information from, and controlling, lower-level DM functions and NEs. Any function that automatically optimizes NE parameters can in principle execute in the NE, DM, or the NM.
Functions that automatically monitor network operations and parameters, and user actions, and automatically take actions to optimize network operations are referred to as Self-Organizing Network (SON) functions. SON functions are also structured hierarchically—with a high-level SON function (for example, a NM) operating to optimize the overall network, and a plurality of lower-level SON functions (for example, at each NE) locally optimizing the NE, under the control and direction of the high-level SON function. The terms “high-level SON function,” “network manager (NM)” or “network management system (NMS),” and “centralized SON function” are used synonymously herein. Similarly, “lower-level SON functions” are sometimes referred to as “network element (NE)” SON functions or “distributed” SON functions.
The SON functions may vary depending on the time scale on which they operate (e.g., ranging from seconds/minutes level to hours/days level), the target parameter set, and the type of optimization that they execute. For example, SON functions that require fast operation and/or dealing with individual per user actions are typically deployed in the network, close to the radio interface. Other functions that operate on a longer time scale and dealing with cell level optimizations can be deployed higher up in the management system.
To support interaction between SON functions in the network and the OAM system (or between lower-level SON functions and a high-level SON function) there exists a minimal set of control functions defined and standardized by 3GPP. This includes, for example, the setting of target parameters for network SON functions or specifying the importance of one target as compared to others via assigning priorities (see, for example, Section 4.7 of TS 32.522, V11.1.0, 2011-12, for more details).
The 3GPP standard also defines notification procedures on the Itf-N interface, which can be used by the DM to notify the NM when some configuration parameters have been changed in the network. This can help the NM to get an up-to-date view of the network configuration, covering, for instance, cases when the NE SON function has changed certain cell parameters. However, the indication does not reveal which function has changed this parameter (e.g., which SON function) or the specific reason of the change.
Although, the different SON functions deployed in different parts of the system (i.e., in the NE, in DM or NM) typically have different scope and targeting different sets of parameter tuning, it is not possible and not even desirable to avoid overlaps completely. Partly, this is due to the fact that the same problem, showing the same or similar symptoms could be solved in different ways by different SON algorithms. For example, load balancing may be executed by forced handover of users between neighboring cells, which can be executed by a SON function in the RAN or it could be executed by changing the cell sizes via antenna tilting from the OAM system.
Currently there is no solution specified for information exchange between SON functions at different hierarchical levels, i.e., lower-level SON functions in the network and high-level SON function in the OAM, that would be sufficient to resolve conflicts and avoid interference between the different SON functions. The currently defined Performance Measurements (PM) (i.e., counters, Key Performance Indicators (KPI), events) are not sufficient for the observation of the actions and the operation of lower-level SON functions from the high-level SON function. The notification mechanisms defined in the standard for indication of network parameter changes are not sufficient for SON coordination purposes, as they do not cover notification of actual SON actions, and do not reveal which function has initiated the reconfiguration and for what reason.
This means that the SON functions at different hierarchical levels must act “blindly” in the sense that they do not have information regarding the actions of the other SON functions working on the same or similar objective. This could result in a situation wherein one SON function nullifies the effect of the other SON function, or the two SON functions get stuck in a suboptimal solution.
Accordingly, there is a need for a technique that improves the interaction among hierarchically arranged SON functions.
The Background section of this document is provided to place embodiments of the present invention in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.